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Group IIA - Coggle Diagram
Group IIA
Extraction
Thermal reduction of quicklime (CaO) from
limestone (CaCO3)
- CaCO3 --->CaO + CO2
- 2CaO + Al ---> Ca + Ca2Al2O2
- Sr and Ba is extrated by electrolysis of their molten
chlorides
Trend in Melting Point
Decreases down the group
- Each atoms contribute two electrons to the delocalised cloud
metallic bonding gets weaker due to the increased size of ion
- Group 1 metals have lower melting point that the Group 2 metal
because each metal only contributes one electron to the cloud
- Magnesium doesnt fit the trend because crystalline structure can also effect the melting point of a metal
Trend In Reactivity
The reactivity of alkali metals increases down the group
- The size of the element’s atoms, and the
number of full electron shells, increases down
the group.
- This means that, down the group, the electron
in the outer shell gets further away from the
nucleus and is shielded by more electron shells
- The further away an electron is from the positive
attraction of the nucleus, the easier it can be
lost in reactions.
- This means that reactivity increases with the
size of the atom
General Properties
Halide of metals : give colour when heated
- Ca^2+ :brick-red
- Sr^2+:red
- Ba^2+:yellowish-green
Chemical reaction
ACID
- the reaction is more vigorous as we go down the group
- H2 evolve and forming salt
- M + 2HNO3 ---> M(NO3)2 + H2
M=Be:passive towards HNO3 due to the formation of the stable oxide on metal surface
Application
Beryllium
- Alloy
- As a moderator
- X-ray windows
Magnesium
- Bombs
- Used in flash photography
- Alloys
- Reducing agent
- Medicine
- Firework giving white light
Physical properties
- All metal oxides are ionic (except for BeO)
- Solubility of the oxide increases from Be ---> Ba
- All oxides are base (except for BeO, Amphoteric)
Preparation
MgCO
- Mg(NO3)2 + 2NaHCO3 ---> MgCO3 + 2NaNO3 + H2O + CO2
- Cannot use Na2CO3 because it is too basic compared to NaHCO3 and will produce basic magnesium carbonate: Mg(OH)2.MgCO3
Carbonates
Stability of the oxyanion
- Increases down the group
- strength of ionic bonding between cation and
anion decreases resulting in the increase of bond
strength between the atoms in oxyanion molecule
- The increase of the size of oxyanion causes the
repulsion between the atoms in the oxyanion molecule
Hard and Soft water
- Soft Water:Water which contain the only cation (positively charged ion) Na+
- Hard water:Water which contain an appreciable
quantity of dissolved minerals such as Mg^2+ and Ca^2+ ions
-
-
Diagonal Relationship
- Both form covalent hydride and halides ; the rest of group IIA are
predominantly ionic
- Both form amphoteric oxides : oxides of the rest of the group II are
basic
- In the present of access OH ion, both form [ Be(OH)4]^2- and [Al(OH)4]^- (soluble)
- Both form structure based on linked tetrahedra
- Both form carbides that contain C^4- and produce methane on
reaction with water
- Be2C + H2O ---> BeO + CH4
- AL2C3 + H2O ---> Al2O3 + CH4
- Group 2 carbide contain C2^2- and produce ethyne when react with water